This invention relates generally to a pressure balance system between a set of dual tires on a vehicle and more specifically to a valve arrangement for controlling the air pressure between such dual tires.
Load hauling trucks, earthmoving equipment, and the like often are propelled by sets of dual tires. Machines of this nature typically have a set of dual tires mounted on each end of an axle. Each set of dual tires includes an inner tire and an outer tire, with each tire being mounted on a separate rim. The inner rim and tire are attached to an inboard end of a wheel assembly and the outer rim and tire are attached to an outboard end of the wheel assembly. The wheel assembly rotates about an axle via a pair of wheel bearings. One of the wheel bearings is located near the inboard end of the wheel assembly and the other is located near the outboard end of the wheel assembly. The wheel bearings are designed and positioned on the axle to carry a predetermined portion of the load (gross weight) of the machine, the load is then transferred through the tires to the ground. During normal operation of the machine, the air pressure in the inner and outer tires may not be equal. This can be caused by improper inflation, uneven heating of the tires, or an air leak in either tire.
Unbalanced or improper air pressure between the inner and outer tires can cause a portion of the load on either wheel bearing to shift from one bearing to the other. These unbalanced loads can cause excessive wear on one or each of tire(s) or improper loading on one or each of the wheel bearing(s). Repeated excessive loading may cause permanent damage to the bearing(s).
Each of the tires could be connected together by a hose or tube passageway to allow equalization of air pressure, but a sudden loss of pressure in either tire would result in a loss of pressure in both tires.
This invention is directed to overcome one or more of the problems set forth above.
In one aspect of the present invention, a pressure equalizing valve is provided for equalizing the air pressure between a set of dual tires. The equalizing valve has a pair of piston chambers. Each piston chamber has an inlet port, outlet port, and a piston reciprocatably positioned within its respective piston chamber. The piston is moveable between a first and a second position where the first position closes the outlet port and the second position opens the outlet port. The outlet ports of the piston chambers are connected together to allow passage of air when each piston is in its second position. A biasing arrangement in each piston chamber acts to move its respective piston toward its first position while air pressure at the respective inlet port acts to move the piston toward the second position.
In a second aspect of the present invention, a method is provided for equalizing the air pressure between a pair of tires. The method includes determining if the pressure in each tire is above a predetermined minimum, providing airflow between the tires if each tire is above the predetermined minimum, and preventing airflow between the tires if either tire is below the predetermined minimum.